A central venous catheter (CVC) is an intravenous access into the central, large-vein portion of a person's blood stream. A CVC provides a way of injecting medication or sampling blood very near to the person's heart. A CVC thus includes an access lumen to which is connected an injection port in the form of a pierceable rubber membrane. Fluid transfer through the CVC requires first cleaning the pierceable membrane with alcohol and/or Betadine and then inserting a hypodermic syringe needle through the membrane. This provides direct access to the patient's blood stream.
The pierceable membrane is often provided as part of a removable injection port. Conventional luer-lock connectors allow removable mating or hook-up between the CVC and the injection port. Thus, an alternative method of accessing the CVC is to remove the injection port and attach a syringe tip directly to the CVC access lumen.
The main purpose of a CVC is to allow fluid injection and withdrawal to and from a patient's blood stream. A CVC is placed in a patient by surgical procedure, and is attached to the skin by sutures. A CVC is often left in place for a relatively long time. The skin entry point is kept covered by a carefully monitored dressing. Because of the direct nature of access into a patient's blood stream, infection control when dealing with CVCs is of utmost importance. In most institutions, only registered nurses and doctors are allowed to perform procedures relating to CVC access.
CVC access lumens can become clogged by clotted blood. Accordingly, such lumens are kept open by injecting a Heparin solution into them. Heparin is a protein material which acts as a blood anti-coagulant to interfere with blood clotting. Before transferring fluid to or from a patient through the CVC, it is sometimes desired or necessary to remove this Heparin and the blood containing such Heparin.
There are significant risks associated with transferring fluid through a CVC. One risk is that of microbial infection. Another significant risk is that of air embolism. Both of these risks are potentially life-threatening and increase significantly with each hook-up through the CVC access lumen, especially when such a hook-up is by way of a needle and pierceable membrane. Compounding these risks is the fact that a single medication injection procedure or a single blood collection procedure can require four or more hook-ups to the CVC access lumen, one for each separate fluid injection and withdrawal through the CVC access lumen. In some cases, the CVC is used for medication injection or blood withdrawal as many as four to six times each day. Thus, as many as 24 hook-ups are required every day, with a corresponding number of opportunities for infection or air embolism. Over the period of a month, the CVC could present over 700 opportunities for life-threatening events to occur.
As an example, a simple medication injection procedure requires the following steps. First, the pierceable membrane of the injection port must be cleaned with alcohol. The success of this step is highly dependent on the skill of the care-giver and is subject to mistakes caused by carelessness or inattentiveness. A waste blood withdrawal device such as a hypodermic syringe is subsequently prepared and its needle inserted through the membrane. The syringe is operated to withdraw Heparin-containing blood from the CVC. A medication syringe is then prepared, its needle inserted through the pierceable membrane, and medication injected into the CVC. Subsequently, a "flush" syringe is prepared with sterile saline solution. The sterile saline is injected through the pierceable membrane into the CVC to carry the medication into the patient's blood stream. Finally, a Heparin syringe is prepared and Heparin is injected into the CVC through the pierceable membrane to prevent clotting.
Withdrawing or collecting blood requires similar steps. First, Heparin or Heparin-containing blood is withdrawn from the CVC transfer lumen by injecting a needle through the pierceable membrane and withdrawing blood into a syringe. A blood withdrawal syringe or other blood collection device is then prepared and its needle inserted through the CVC pierceable membrane. After a sufficient amount of blood is withdrawn, the blood withdrawal syringe is removed. First a normal saline flush of 20 milliliters is injected, then a Heparin syringe is prepared and its needle inserted through the pierceable membrane. A prescribed amount and concentration of Heparin is injected into the transfer lumen to prevent subsequent blood clotting.
As is apparent from the above discussion, another problem with standard CVC access procedures is that the various solutions and syringes needed to access a CVC are supplied separately. Often, a nurse must track down each piece of equipment separately. This can be a costly and time consuming process. Furthermore, even after proper equipment is found, such equipment is often not designed to work together as a system.
Because of this, CVC procedures often require more than one person. Since CVC operations are performed only by registered nurses or doctors, the time expended by these persons is relatively valuable. In addition, other personnel are often forced to remain idle while waiting for the qualified persons to find time to provide the service.
As an additional complication, access to a CVC by needle gives rise to a potential source of injury and infection to the care giver through contact with the needle. This is particularly important when the patient being treated has a dangerous infection, such as HIV or Hepatitis. Often, even the care giver is unaware that the patient has such as infection.
Blood withdrawal through a CVC involves additional problems. A blood collection device is often in the form of a conventional plunger-type syringe. However, subsequent processing of blood cannot take place in such a syringe. Accordingly, it is necessary to transfer blood from such a blood collection syringe to a suitable container for centrifugal processing or other treatment. Furthermore, it is often desirable to have a reagent such as an anti-coagulant within the blood collection device prior to blood collection.
A "Vacutainer blood withdrawal tube" is often used to alleviate the blood collection problems noted above. A Vacutainer blood withdrawal tube is an evacuated tube which is suitable for use in subsequent blood processing steps. It has a forward end which can be connected to a hypodermic needle or mating connector which is in turn connected to a source of blood. Once connected, the vacuum within the Vacutainer blood withdrawal tube draws blood into the container. However, Vacutainer blood withdrawal tube have their own problems. For instance, it is impossible when using a Vacutainer blood withdrawal tube to regulate the amount of withdrawing pressure imparted to a patient's blood stream. The initial vacuum is usually quite high, and is applied very suddenly. Thus, collapse of or damage to veins often results from the initial connection of the Vacutainer blood withdrawal tube to a vein or blood vessel.
The invention described below reduces the number of sequential connections which are required to administer medication or to withdraw blood through a CVC. In addition, several embodiments of the invention completely eliminate hypodermic needles from the process. Furthermore, an improved blood collection device is disclosed for connection to the CVC access system. The improved blood collection device eliminates the problems noted above and exhibits additional desirable characteristics which will become apparent. Furthermore, the CVC access system described below is conveniently supplied together as an integrated system, thus reducing much of the work previously associated with CVC operations and procedures.